Spell check on Mac desktop app

Merged

I have an iPhone 6 plus and a Mac computer with Yosemite 10.10.5 and the text messaging on the iPhone works but not on the Mac desktop version. I thought it worked on both before I upgraded to the new 8.3.5.24028 (64-bit) but, I am not sure.

Either way it seems if the iPhone has it the Mac should have it too. Can you tell me if it should have it or if I have an isolated issue please. Also, if it does not have it can you add it soon?